After slaughter, cows over a certain age are presently examined for BSE (bovine spongiform encephalopathy, prion infection) with the aid of an immunological test, e.g., the PRIONICS-Check LIA, PRIONICS-Check WESTERN or PrionScreen BSE assays (PRIONICS is a registered trademark of Prionics AG, Switzerland). The cadaver is released for further processing and allowed to enter the human food chain upon obtaining a negative test result. Part of the brainstem (medulla oblongata), preferably the obex region (FIG. 1), is used as starting material for removal of a tissue specimen with which the test is carried out. Part of the brainstem is removed in the slaughterhouse. By way of the foramen magnum, i.e., the large opening on the posterior of the skull through which the spinal cord emerges, the obex and adjacent areas are removed using a specially shaped spoon and are introduced into a special container. In the container, the brain material is taken to a test laboratory where the actual specimen for establishing a prion infection is removed.
A number of test systems presently available on the market require the analysis to be carried out with a defined quantity of specimen material. The quantity is generally determined by weighing. To do this, manual operations have to be conducted in which potentially infectious material is handled under stringent biological safety conditions. Particularly with a view to safety at work, it is desirable to limit the operations using unsealed brain material. In concrete terms, it would be advantageous to be able to determine the quantity more quickly and more easily since, in this way, more specimens can be fed to a test system per unit of time. This would have a positive impact on the specimen throughput attainable in the laboratory.
In the state of the art there are devices known which were designed for taking samples from tissue or a tissue specimen. However, the state of the art has certain disadvantages.
EP 1 293 167 discloses a cutting device for biopsies comprising a hollow needle with a circular blade. A grid inside the needle limits the amount of tissue which can be taken up by the cavity of the needle. Also inside the needle, between the grid and the opening of the needle a thin wire is stretched between two opposite points at the inner wall of the needle. After the device is pushed into a tissue specimen the needle is twisted, whereby the tissue portion located between the grid and the wire is cut from the remaining tissue specimen. Suction is applied to retain the cut portion of tissue at the grid, thereby allowing removal of the cut portion from the remaining tissue specimen.
US 2004/0116942 discloses a device for extraction of follicular units from a donor area, for the purpose of transplantation into balding areas of the scalp. The device comprises a cylindrical punch to which a perforator is affixed, and a grid as a guard member aimed at containing successfully extracted hair follicles. The punch is described as being a standard biopsy punch with a diameter of 1 mm, corresponding to the size of a single target follicular unit. The punch is used to make a first circular incision around the hair follicle. The perforator is used to make a second, deeper incision to weaken the structural integrity of the surrounding connective tissue without damaging the hair follicle. Subsequently, the follicular unit is extracted using suction. In the device the grid prevents the follicular unit to enter the suction means and be eventually lost.
Other devices for removing tissue parts are disclosed in U.S. Pat. No. 3,990,451 and US 2003/082797.